1. Field of the Invention
This invention relates in general to means and methods for providing closely spaced contacts in semiconductor devices and, more particularly, to means and methods for providing closely spaced contacts in semiconductor devices which employ intermetallic contact regions.
2. Background Art
It is desirable in the semiconductor art to be able to use intermetallic contact regions. These intermetallic contact regions can provide very low resistance ohmic contacts or, alternatively, can provide high quality Schottky contacts.
Intermetallics are generally formed by reacting one or more metallic elements with the semiconductor of choice. For example, in the case of silicon semiconductors, a wide variety of metals such as Pt, Mo, W, Ni, Ti, and Ta are but a few of the many silicide forming materials which are known. Platinum is a particularly convenient intermetallic forming element and is widely used.
A need that often arises in connection with high density integrated circuit structures employing dielectrically isolated semiconductor tubs, is to simultaneously make contact to the device regions within the tub and the tub itself. In the prior art, when silicides or silicide forming materials were employed as a part of the contact structured, additional masking steps were required in order to make separate, non-shorting contacts to the tub and the device regions contained therein. These extra masking steps add to the cost and complexity of the devices. In addition, each masking step requires that provision be made in the device layout for the necessary mask-to-mask alignment tolerance. This increases the area occupied for a given circuit function and further increases the cost. Thus, a need continues to exist for improved processes and structures in dielectrically isolated circuits employing intermetallic contacts which utilize minimum surface area and which can be fabricated with the fewest possible masking operations.
Accordingly, it is an objective of the present invention to provide an improved means and method for forming intermetallic contacts to semiconductor regions wherein separate masking operations for contacting the N and P regions are eliminated.
It is a further object of the present invention to provide an improved means and method for contacting semiconductor devices employing intermetallic contacts wherein N and P-type contacts may be brought as close as the minimum layout line width without requiring any provision for alignment tolerance.
It is an additional object of the present invention to provide an improved means and method for forming intermetallic contacts to semiconductor devices wherein the contacts to the N and P regions are self-aligned.
It is a further object of the present invention to provide the foregoing advantages simultaneously.